1. Field of the Invention
The present invention relates generally to perpendicular magnetic recording heads for applying perpendicular magnetic fields to recording media such as disks having hard layers. More particularly, the present invention relates to a perpendicular magnetic recording head in which the height and the width in the track width direction of a main pole layer are controlled within predetermined ranges and to a method for making the perpendicular magnetic recording head.
2. Description of the Related Art
Perpendicular magnetic recording technology has been applied to recording devices which record high density magnetic data on recording media such as disks. FIG. 28 is a cross-sectional view showing the structure of a typical perpendicular magnetic recording head employed in such a device.
As shown in FIG. 28, a perpendicular magnetic recording head H is disposed on a side face of a slider 1 which floats and moves over a recording medium. For example, the perpendicular magnetic recording head H is disposed on a side face 1a of the slider 1 between a nonmagnetic layer 2 and a nonmagnetic coating layer 3.
The perpendicular magnetic recording head H comprises an auxiliary pole layer 4 and a main pole layer 5 both composed of a ferromagnetic material. The main pole layer 5 is disposed on the auxiliary pole layer 4 with a gap therebetween. An end face 4a of the auxiliary pole layer 4 and an end face 5a of the main pole layer 5 are exposed at an opposing face Ha opposing a recording medium M. The auxiliary pole layer 4 and the main pole layer 5 are magnetically connected at a magnetic connection portion 6 some distance inward from the opposing face Ha.
A nonmagnetic insulating layer 7 composed of an inorganic material such as Al2O3, SiO2, or the like, is disposed between the auxiliary pole layer 4 and the main pole layer 5. An end face 7a of the nonmagnetic insulating layer 7 is also exposed at the opposing face Ha between the end face 4a of the auxiliary pole layer 4 and the end face 5a of the main pole layer 5.
A coil layer 8 composed of a conductive material such as copper is embedded in the nonmagnetic insulating layer 7.
As shown in FIG. 28, the thickness hw of the end face 5a of the main pole layer 5 is smaller than the thickness hr of the end face 4a of the auxiliary pole layer 4. The width of the end face 5a of the main pole layer 5 in the track width direction, i.e., the X direction in the drawing, is a track width Tw. This width is sufficiently smaller than the width of the end face 4a of the auxiliary pole layer 4 in the track width direction.
The recording medium M on which magnetic data is recorded by the perpendicular magnetic recording head H moves in the Z direction relative to the perpendicular magnetic recording head H and has a hard layer Ma on the surface and a soft layer Mb provided under the hard layer Ma.
When the coil layer 8 is energized, a recording magnetic field is induced between the auxiliary pole layer 4 and the main pole layer 5. A leakage recording magnetic field between the end face 4a of the auxiliary pole layer 4 and the end face 5a of the main pole layer 5 perpendicularly passes through the hard layer Ma and the soft layer Mb of the recording medium M. Because the area of the end face 5a of the main pole layer 5 is sufficiently smaller than the area of the end face 4a of the auxiliary pole layer 4, the magnetic flux Φ will be concentrated to the portion of the hard layer Ma opposing the end face 5a of the main pole layer 5. As a result, the magnetic data is recorded on the portion of the hard layer Ma opposing the end face 5a by the magnetic flux Φ.
FIG. 29 is a diagram illustrating a step of a method for making the perpendicular magnetic recording head shown in FIG. 28.
The main pole layer 5 is formed by plating, as shown in the drawing, using a resist layer not shown in the drawing. Subsequently, a portion 9a of a plating base layer 9 formed on the nonmagnetic insulating layer 7, the portion 9a being formed in the region not overlaid by the main pole layer 5, is removed by milling. Thus, the portion 9a is prevented from coming into contact with the lead layer for supplying electric current to the coil layer 8, and the electrical characteristics of the layer can be maintained at a satisfactory level.
However, referring to FIG. 29, during milling of the portion 9a, the top face of the main pole layer 5 is milled as well, resulting in a decrease in the height of the main pole layer 5 from L1 to L2. A decrease in the height of the main pole layer 5 will result in a decrease in the area of the end face 5a and thus degradation of the overwrite characteristics.
Moreover, removing the portion 9a will result in an increase in the track width Tw due to the adhesion of the material constituting the portion 9a onto two side faces 5b of the main pole layer 5, as indicated by arrows B. Adhered layers 9b on the two side faces 5b must be removed.
During removal of the adhered layers 9b by milling in directions A shown in FIG. 29, the top face of the main pole layer 5 is also milled, further decreasing the height of the end face 5a. 
To meet the need for higher-density recording, the track width needs to be reduced. However, even when the track width Tw is reduced by milling the two side faces 5b of the end face 5a of the main pole layer 5 in an angled direction, the top face of the end face 5a is also removed, resulting in a decreased height which will result in the degradation of the recording characteristics such as the overwrite characteristics. Also, controlling the area of the end face 5a within a predetermined range has been considerably troublesome.
As described above, according to the structure of the typical perpendicular magnetic recording head shown in FIGS. 28 and 29, the adhered layers 9b on the two side faces 5b of the main pole layer 5 cannot be removed and the track width of the main pole layer 5 cannot be made smaller while maintaining the main pole layer 5 at a predetermined height. In other words, it has been impossible to separately control the height and the width in the track width direction.